1. Field of the Invention
This invention relates to energizer apparatus for recharging batteries, and, more particularly, to energizer apparatus for recharging flashlight batteries in place within a flashlight.
2. Description of the Prior Art
Small battery powered appliances have been in use for some time, but they have in general utilized non-rechargeable batteries, also sometimes identified or referred to as primary batteries, of the type commonly employed in flashlights. In such cases, the batteries are simply replaced when they have run down. For want of a better product, the expense and inconveniences associated with the replacement of the batteries was tolerated.
The necessity for the periodic replacement of such batteries, however, is more than an economic disadvantage. A more serious disadvantage is the possibility that the appliance when most urgently needed is without battery power. Furthermore, because of the limited shelf-life of such batteries, it is difficult to maintain a stock of reliable spares.
Probably the most commonly employed appliance in this category is the flashlight and because the flashlight is so often employed in emergencies involving personal safety, the limitations of non-rechargeable batteries constitute a serious hazard as well as a nuisance.
The recent availability of rechargeable, also sometimes identified or referred to as secondary batteries, batteries appropriate for flashlights and other small appliances has produced a surge of interest in recharging means for these batteries.
U.S. Pat. No. 2,410,527 describes a battery charger which uses the battery of an automobile as the charging energy source. The charger itself is fabricated in a form suitable for mounting on the instrument panel of an automobile and it utilizes an incandescent lamp as a series element for the limitation of charging current. Batteries are removed from the flashlight and placed in the charger to be recharged.
U.S. Pat. No. 3,021,466 describes a flashlight with a built-in charger designed to be plugged into an alternating current (ac) source outlet for recharging. The recharging circuit in this case is simply connected across the battery incorporating appropriate rectifying and current limiting elements but neglecting the use of an isolation transformer as a safety measure.
U.S. Pat. No. 3,217,224 describes a device for the recharging of flashlight batteries without removing the batteries from the flashlight. The flashlight is specially designed to permit external access to the battery terminals. An external incandescent lamp is again employed as a current limiting element.
U.S. Pat. No. 3,829,676 describes a rechargeable flashlight and a charger for the flashlight. The end cap of the flashlight includes an aperture extending through the bottom wall and a metal plate within the end cap biased against the end cap and covering the aperture. The charger receives the end cap of the flashlight and includes an upwardly projecting plug which extends through the aperture and against the metal plate. The flashlight is biased in the charger by the camming action of the front of the flashlight against a sloping wall on the front of the charger. The camming action thus insures that the plug will extend into the end cap.
The arrangement of the apparatus of patent 3,829,676 is vulnerable to potential problems in at least two respects. First, the upwardly projecting plug in the charger may be accidentally bumped or knocked out of alignment, which would prevent its extending through the aperture in the end wall. Second, dirt, rain water, or other foreign matter may enter the aperture and prevent electrical contact between the contact plate and the metal end cap, thus preventing the flashlight from operating as a flashlight due to an open circuit. If such dirt, rain water, or other foreign matter enters the end cap through the aperture, the end cap must be removed from the flashlight and disassembled in order to remove the material and clean the end cap.
More recently, certain small battery powered appliances have been designed for recharging from an ac source utilizing a charger socket which magnetically couples energy into the appliance. Such means are not, however, practical for use in an automobile where only direct current (dc) power is available.
While the prior art device notably advance the state of the art, certain important features are still lacking. As U.S. Pat. No. 3,217,224 points out, there is a need for providing a high degree of user convenience which will assure that the batteries are regularly recharged. This implies that provision be made for the recharging of the batteries without removal from the flashlight. Furthermore, the recharging unit should be carefully designed mechanically to facilitate the removal of the flashlight from the charger. The appearance of the device must be suitable to permit its installation in exposed locations where the charger can serve as a storage means for the flashlight. Finally, the charger should preferably be adapted to ac or dc power sources so that it may utilize either the utility outlet in the home or the battery of an automobile depending upon the intended use of the flashlight. An additional desirable feature not suggested in the prior art is a means for adapting an existing flashlight or related device to charger use.